JPH07154990A - Motor speed controller - Google Patents

Abstract

PURPOSE:To obtain a motor speed controller which can prevent misdetection of speed data due to a delay of updating detection data of speed during low- speed rotation even by using a low-cost and small-sized encoder. CONSTITUTION:This controller has a cycle detection means 1 which measures a cycle of encoder signals by counting clock signals, an arithmetic device 2, a data holding means 3, and a correcting means 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed control device, and more particularly to a motor speed control device for controlling the speed of a motor according to a deviation between a motor speed command signal and a motor speed signal detected by an encoder. .

[0002]

2. Description of the Related Art Conventionally, as an example of a motor speed control device for controlling the speed of a motor according to a deviation between a motor speed command signal and a motor speed signal detected via an encoder, there is an invention disclosed in Japanese Patent Laid-Open No. 2-119591. is there.

The above invention, as shown in FIG. 5, is a motor speed control device for controlling a motor speed in accordance with a deviation between a motor speed command signal and a motor speed signal detected through an encoder. A clock generating means for generating a signal, a means 26 for measuring the cycle of the encoder signal by counting the clock signal, a means 28 for integrating the cycle over a predetermined period, and a sampling period asynchronous with the predetermined period. And a means 30 for detecting the number of pulses of the encoder signal within the sampling period, the integer part and the decimal part of the number of encoder pulses within the sampling period are calculated, and the motor speed is calculated by correcting the encoder pulse number. Has been done.

In such a configuration, when the motor speed is calculated using the encoder pulse frequency, the encoder pulse for a predetermined period for integrating the encoder pulse period is obtained, and the number of encoder pulses within the sampling period asynchronous with the predetermined period is obtained. The motor speed is calculated by calculating the integer part and the fractional part of, and correcting the encoder pulse number.

As shown in FIG. 6, the encoder pulse number n within the sampling period T (corresponding to the period of the sampling signal E) may be obtained. However, the number of pulses within the sampling period T is not exactly n, but n. Since it is smaller, the clock count number corresponding to the encoder signal period is t and the time of n encoder pulses in the T period is tn in order to obtain the integer part and the decimal part, and f = (1 / T) · (n− 1+ (T-tn) / t) to find the frequency. Therefore, the motor speed v
Becomes v = A · (1 / T) · (n−1 + (T / tn) / t), where A is the conversion constant.

In FIG. 6, (t1 + t2) / t
Corresponds to the fractional part of the number of encoder pulses in the sampling period T, and the detection accuracy is related to the measurement accuracy of t. When calculating the motor speed using the encoder pulse cycle, tn / (n-1) is calculated and the average value of the pulse cycle is calculated. Therefore, the motor speed v in this case is v = A '. (N-1) / tn, where A'is the conversion constant.

[0007]

However, the above-mentioned prior art has the following drawbacks. That is, although there is an effect that the detection accuracy of the motor speed can be improved by using the encoder signal frequency and the data of the cycle and the detection accuracy can be made substantially constant over a high range of speed, the motor speed is very low. When rotating at the speed, since the encoder pulse is not detected within the sampling period, the encoder pulse cycle is not detected and the speed data is not updated until the next pulse is input.

That is, the speed at the time of sampling cannot be measured when the encoder pulse never enters the sampling period, and the past speed is used to substitute the actual speed. Therefore, for example, even when the motor is stopped, speed detection data indicating that the motor is rotating is output, which causes a slight vibration. Also, as a method of solving the above-mentioned drawbacks,
It is possible to increase the number of encoder pulses,
As a result, the cost of the encoder becomes extremely high and the size of the encoder becomes very large.

Therefore, the present invention has been made in view of the above-mentioned drawbacks of the prior art. Even if an inexpensive and small encoder is used, erroneous detection of speed data due to a delay in updating speed detection data at low speed rotation can be prevented. It is an object of the present invention to provide a speed control device for a motor capable of controlling the motor.

[0010]

FIG. 1 is a block diagram showing the present invention. According to the present invention, in a speed control device in which a speed controller 5 controls the speed of a motor 7 via a power amplifier 6 in accordance with a deviation between a motor speed command signal and a motor speed signal detected via an encoder 8, a cycle of an encoder signal is used. Clock generation means (not shown) for generating a measurement clock signal, cycle detection means 1 for measuring the cycle of the encoder signal by counting the clock signal,
An arithmetic unit 2 for calculating the speed from the cycle, a clock generating means (not shown) for determining the speed detection sampling period, the latest sampling data in the speed detection sampling, such as a memory, and at least one previous sampling data. When the data holding means 3 for holding the data and the data holding means 3 for the cycle measurement data are not updated because the encoder pulse is not input within the speed detection sampling period, the speed detection value is corrected using the sampling time. The correction means 4 is provided.

[0011]

In the present invention, in order to measure the cycle of the pulse signal of the encoder 8 mounted to detect the speed of the motor 7, the speed calculating device calculates the cycle signal from the data obtained by counting the cycle measuring clock signal. 2 is converted into velocity data. The converted speed data is output as a speed detection value for obtaining a speed deviation for each speed detection sampling time, and at the same time stored in the data holding means 3. The data holding means 3 always holds the latest sampling data and at least the previous sampling data.

If the latest speed sampling data sampled and held is the same as at least one previous speed sampling data, it is determined that the data has not been updated by the encoder signal within the speed sampling period, It is considered that the motor 7 is slower than the detected data or stopped, and the speed is corrected by the correction means 4 which corrects the speed by regarding the reciprocal of the sampling time as the current rotation speed of the motor 7.

[0013]

Embodiment 1 FIGS. 2 and 3 show the present embodiment, FIG. 2 is a block diagram, and FIG. 3 is a signal waveform diagram of speed correction calculation.
This embodiment will be described with reference to FIG.

In a speed control device in which the speed of the motor 7 is controlled by the speed controller 5 through the power amplifier 6 in accordance with the deviation between the motor speed command signal and the motor speed signal detected by the encoder 8, the cycle of the encoder signal is measured. Clock generator (not shown) for generating clock signals
A cycle detector 11 for the encoder signal, a speed calculator 12 for calculating a speed from the cycle, a clock generator (not shown) for determining a speed detection sampling period, the latest sampling data in the speed detection sampling, and The memory 13 that holds at least one previous sampling data, the comparator 14 that compares the latest sampling data with the previous sampling data, and the comparator 14 count up when it is determined that they are the same, A counter 15 that clears the count value when it is determined that they are not the same, a divider 16 that divides the data of the period detector 11 by the sampling time, a comparator 17 that compares the data of the counter 15 and the data of the divider 16, and a counter 15
Correction speed calculator 18 that calculates a speed correction value based on the data of S. and the sampling time, and a switch 19 that switches between the correction speed data and the speed data obtained from the signal of the encoder as the detection data. .

In this embodiment, in order to measure the cycle of the pulse signal of the encoder 8 attached to detect the speed of the motor 7, the speed is calculated from the data obtained by counting the cycle measuring clock signal by the cycle detector 11. Device 1
2 is converted into velocity data. The converted speed data is output as a speed detection value for obtaining a speed deviation for each speed detection sampling time, and at the same time, the memory 13
Stored in. The memory 13 always holds the latest sampling data and at least the previous sampling data. The latest velocity sampling data and the immediately preceding velocity sampling data are compared by the comparator 14, and it is determined whether or not they are the same. If they are the same, the counter 15 counts up, and if they are not the same, the count value of the counter 15 is cleared.

The data of the period detector 11 and the sampling time are input to the divider 16, and the number of sampling periods between the pulses of the encoder 8 is calculated by dividing the period data by the sampling time. The correction speed calculator 18 calculates the correction speed by multiplying the data of the counter 15 by the sampling time and taking the reciprocal thereof. The comparator 17 compares the sizes of the data of the counter 15 and the data of the divider 16, and when the counter value is larger, the corrected speed data is input, and when not, the latest data is output. Switch 19
You can switch with.

The method of speed correction will be described below with reference to FIG. In the case where the encoder pulse does not enter during the speed sampling period, such as between S3 and S4, the speed data calculated from the Te1 cycle data when the E1 pulse is detected becomes the latest data. However, the actual speed of the motor is calculated from the cycle of Te2 and is lower than the speed of Te1, and the speed information at the time of sampling in S3 is different from the speed of Te1. Therefore, assuming that the speed is the same as the speed of Te1 in the sampling after S3, the speed data of Te1 is used in the sampling between Te1 ', that is, in the sampling of S3 and S4.

However, since it is clear that the speed is low in the sampling after S5, the speed correction value described below is used as the detection data. As a method of calculating the speed correction value, the period of the encoder pulse is replaced with the sampling period, and for example, in the case of S5 sampling, (Ts3 + Ts4) is set as the period for speed detection, and in the case of S6 sampling, (Ts3 + Ts4 +
Ts5) is a period for speed detection, and its reciprocal is speed detection data. That is, for the speed data when the motor speed is low, the sampling time is Ts, the counter 15
If m is the data of, it can be corrected as the reciprocal of (Ts × m).

According to this embodiment, the speed can be detected without deteriorating the speed detection sampling time.

[0020]

Second Embodiment FIG. 4 is a software flowchart showing the present embodiment. Example 1 is different from Example 1 in the following points. The correction means 20 in FIG. 2 is composed of software.

The period data of the encoder is fetched and the latest sampling data and the previous sampling data are compared. If they are not the same, the latest sampling data is saved in the memory as the previous sampling data, and the speed is calculated from the pulse period. When the latest sampling data and the previous sampling data are the same, the sampling number N is calculated assuming the future speed from the past encoder pulse period, and the sampling number counter S is counted up. When the sampling number counter S is smaller than the sampling number N, the velocity is calculated from the pulse period, and when it is larger, the velocity is calculated by the correction velocity calculation using the sampling time.

According to the present embodiment, since it is configured by software, no special hardware is needed.

[0023]

As described above, according to the motor speed control device of the present invention, even if an inexpensive and small encoder having a small number of encoder pulses is used, the speed detection data update delay at low speed rotation may be delayed. False detection can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing the present invention.

FIG. 2 is a block diagram showing a first embodiment.

FIG. 3 is a signal waveform diagram showing the first embodiment.

FIG. 4 is a flowchart showing a second embodiment.

FIG. 5 is a block diagram showing a conventional example.

FIG. 6 is a signal waveform diagram showing a conventional example.

[Explanation of symbols]

 1 cycle detection means 2 speed calculation device 3 data holding means 4 correction means 5 speed controller 6 power amplifier 7 motor 8 encoder

Claims (1)

[Claims] 1. A speed control device for controlling a speed of a motor according to a deviation between a motor speed command signal and a motor speed signal detected via an encoder, and a clock generating means for generating a clock signal for period measurement of an encoder signal. A cycle detecting means for measuring the cycle of the encoder signal by counting the clock signal, an arithmetic unit for calculating a speed from the cycle, a clock generating means for determining a speed detection sampling period, and a latest in the speed detecting sampling. Holding means for the sampling data and at least one previous sampling data, and speed detection using the sampling time when the period measurement data holding means is not updated due to no encoder pulse input during the speed detection sampling period. Equipped with a correction means for correcting the value A motor speed control device characterized by the above.